So far, many theories have been suggested, such as (1) imbalance of hormones, (2) genetics, (3) circulatory failure, (4) nutrition, as the origin of androgenic alopecia.
And it has been also suggested that testosterone (androgenic hormone) played an important role on the generation of hair.
The theory of Adachi at al in which the relation between testosterone and androgenic alopecia is proved by biochemical experiments, is as follows:
i) first, testosterone biosynthesized in testes is converted into dihydrotestosterone by 5.alpha.-reductase existing in hair follicle, sebaceous gland etc. in the head. PA1 ii) dihydrotestosterone reduces the activities of adenyl cyclase remarkably. PA1 iii) it decreases cyclic-AMP in cells. PA1 iv) last, it induces lowering of energy generation of hairs and limbus and supressing of protein synthesis PA1 Japanese Patent Kokai No. 60-97946, PA1 Japanese Patent Kokai No. 60-116657, PA1 Japanese Patent Kokai No. 60-142936, PA1 Japanese Patent Kokai No. 60-142941, PA1 Japanese Patent Kokai No. 60-146855, PA1 Japanese Patent Kokai No. 61-126061, i.e. the European Patent Publication No. 173516, PA1 Japanese Patent Kokai No. 62-198652 and PA1 Japanese Patent Kokai No. 62-198653.] PA1 B.sup.a represents a bivalent group --O--CH.sub.2 -- and PA1 R.sup.a1 represents a group of the formula: ##STR4## (wherein R.sup.a5 and R.sup.a6 represent, independently, a hydrogen atom, a halogen atom or alkyl, alkenyl or alkynyl group of from 1 to 20 carbon atoms(s) which may be replaced optionally from 1 to 5 carbon atoms, by an oxygen atom, sulfur atom, halogen atom, nitrogen atom, benzene ring, thiophene ring, naphthalene ring, carbon ring of from 4 to 7 carbon atoms, carbonyl group, carbonyloxy group, hydroxyl group, carboxyl group, azide group or nitro group) PA1 T.sup.a represents a oxygen atom, PA1 R.sup.a2 represents a hydrogen atom, PA1 R.sup.a3 represents a hydrogen atom, PA1 R.sup.a4 represents a group of --(CH2).sup.ap --COOR.sup.a8 PA1 R.sup.b3 represents a chemical bond together with R.sup.b4, PA1 X.sup.b represents a halogen atom, lower alkyl group, PA1 lower alkoxy group or cyclic alkyl group, PA1 bn represents an integer of from 1 to 3, PA1 R.sup.b5 represents a hydrogen atom and PA1 Y.sup.b represents an oxyalkylene group binding benzene ring via an oxygen atom.] PA1 B.sup.c represents a bivalent ethylenic hydro-carbon of from 1 to 5 carbon atom(s), PA1 R.sup.c represents a hydrogen atom, PA1 R.sup.cl represents one or two substituent(s) selected from alkyl, cycloalkyl, aryl, aralkyl, halogen, alkoxy, aryloxy and alkylthio group and Z.sup.c represents an oxygen atom.]
(See Biochem. Biophys. Res. Commun., 41, 884 (1970)
According to the theory it is thought that, as the result of the series of phenomena, hairs in the growing phase shift to the resting phase, the terminal hairs change to the soft hairs, and the androgenic alopecia develops in the end.
A report by H. V. Schweikert supports this theory that large quantities of metabolites by 5.alpha.-reductase such as dihydro testosterone etc. in hair follicles of the androgenic alopecia-patient exist more than that in females or healthy males. (See J. Clin. Endocr., 38, 811 (1974))
It was reported that dihydrotestosterone converted from testosterone by 5.alpha.-reductase also plays in an important physiological role in the generate of acnes (acne, pimple etc.) other than androgenic alopecia. J. B. Hay et al reported that the metabolism of testosterone by 5.alpha.-reductase was enhanced in the affected part of acne aggravated, from the study in the flux between affected skin of the acne-patient and healthy skin (See Br. J. Dermatol., 91, 123 (1974)).
G. Sansone et al found that the synthetic ability of dihydrotestosterone from testosterone developed from two to twenty times in the affected part of an acne-patient compared to that in healthy man, and they suggested that dihydrotestosterone generated by 5.alpha.-reductase is closely related to the generation or aggravation of acne (See J. Invest. Dermatol., 56, 366 (1971)).
And, dihydrotestosterone is related to the hypertrophy of the prostate. Cowan et al reported that much dihydrotestosterone existed in the prostate of a prostatic hypertrophy-patient (See J. Steroid Biochemistry, 11, 609 (1979)). Recently, it was learned that activity of 5.alpha.-reductase in prostate of a prostatic hypertrophy-patient aggravated abnormally (See J. Clinical Endocrinol and Metabolism, 56, 139 (1983)).
From this informations it is clear that dihydrotestosterone plays an important role in the generation and development of prostatic hypertrophy.